The overall objective is to define the mechanism by which cyclic 3',5' guanosine monophosphate (cyclic GMP) aids in communicating biological signals to target cells and in modulating the specific cellular functions affected by hormones and other biologically active substances. The specific objectives of this proposal are to define the mechanisms by which guanylate cyclase catalyzed generation of cyclic GMP is regulated and to identify and determine the functions of the cellular components with which cyclic GMP interacts in bringing about alterations in specific cellular processes. Mechanisms underlying guanylate cyclase regulation will be studied by characterizing "soluble" and salt extracted "solubilized" forms of the enzyme, examining the role of phospholipids by titration and replacement procedures and by several procedures that should develop an understanding of the involvement of biological oxidation-reduction reactions in the regulation process. The latter will include examining the effects on cyclic GMP metabolism and on guanylate cyclase activity of mitogens and periodate as they effect lymphocyte proliferation and cytotoxicity; arachidonic acid, endoperoxides and ascorbic acid as they affect platelet function; and insulin and several oxidants as they effect fat cell metabolism. The identity and function of specific calcium-dependent cyclic GMP binding proteins will be ascertained through procedures which will permit the detection of cellular proteins complexed with endogenous cyclic GMP and exogenous labeled cyclic GMP. Purified cyclic GMP binding subunits and "holocomponents" will be examined for their ability to catalyze or modulate phosphoprotein phosphatase and phosphotransferase reactions with identifiable enzyme proteins substrates involved in glycogen metabolism.